Steel sheets having excellent rust resistance

ABSTRACT

A steel sheet having excellent rust and corrosion resistance, comprising 0.001-0.15% C, 0.01-1.04% Si, 0.01-1.0% Mn, 0.0010.05% Al, 0.01-0.5% Cu, 0.001-0.04% P, 0.002-0.07% S and Ce in an amount to maintain the weight ratio of Ce/S between 0.1-50, with the balance being iron and unavoidable impurities.

United States Patent 1 Okada et a1.

1 Dec. 30, 1975 4] STEEL SHEETS HAVING EXCELLENT RUST RESISTANCE [75] Inventors: Hideya Okada, Yokohama; l-laruo Shimada, Tokyo, both of Japan [73] Assignee: Nippon Steel Corporation, Tokyo,

Japan 22 Filed: Dec. 19,1974

21 Appl.No.:534,579

Related US. Application Data [63] Continuation of Ser. No. 358,305, May 8, 1973,

abandoned.

[30] Foreign Application Priority Data [58] Field of Search;..... 75/123 E, 124, 125, 126 D, 75/126 0,126 P, 128 E, 128 F, 128 T [56] References Cited UNITED STATES PATENTS 2,861,908 11/1958 Mickelson et a1 75/128 E 3,310,441 3/1967 Mandich 148/36 3,711,340 1/1973 Korchynsky et a1. 75/124 Primary Examiner-L. Dewayne Rutledge Assistant ExaminerArthur J. Steiner Attorney, Agent, or Firm-Toren, McGeady and Stanger [57] ABSTRACT A steel sheet having excellent rust and corrosion resistance, comprising 0.001-0.15% C, 0.01l.04% Si, 0.011.0% Mn, 0.00l0.05% Al, 0.01-0.5% Cu,

- 0.0010.04% P, 0.002-0.07% S and Ce in an amount to maintain the weight ratio of Ce/S between 0.l50, with the balance being iron and unavoidable impurities.

3 Claims, 2 Drawing Figures US. Patent Dec. 30, 1975 3,929,472

75 Proporiion(lo) of undissolved sulfide remaining in water Temperoiure of woier C Proporiion W) of undissolved sulfide remaining in blue dye solution Temperaiure of Solution C sTEEL SHEETS HAVING EXCELLENT RUST RESISTANCE during the production process or during transportation to users, these steel sheets have been often damaged by rust formation, and clarification of its causes and appropriate measures therefore have been sought for by the steel maker, and improvement of corrosion resistance, in addition of prevention of the rust formation has been demanded by users particularly for making Coca Cola cans.

The present inventors have conducted extensive studies on causes of rust formation to find measures to satisfy the above two demands, and as the result it has been found for the first time that the rust formation on commercial steels develops in the following process, and this process of rust formation has been clarified by a unique method for determining the physical properties of sulfides present in the steel (the sulfides are separated by electrolytic extraction to clarify their physical properties, for example their solubility in water, etc.). The process of rust formation on commercial steels progresses as under.

When dews are formed on the steel sheet, first sulfides 0: (Mn, Fe) S present in the steel are dissolved into the dews, and then dissolved Mn and Fe are oxidized by oxygen in water and Mn'** and Fe precipitate as 2Mn O and FeOOl-I, which act as nuclei for formation of 'y Mn,o,.

Then, the thus formed 7 Mn O is dispersed rapidly on the steel surface as colloidal particles and also settles as dispersed colloids around 0: (Mn, Fe) S which has not yet taken remarkable change so that ring-like sediments settle around a(Mn, Fe)S or original a(Mn, Fe)S. These sediments easily adsorb water and thus causes subsequent wet corrosion reaction and results in the formation of red rust of 'yFeOOl-l. Therefore, in order to prevent or reduce such rust formation, it is necessary to reduce the sulfur content in the steel as low as possible so as to reduce a(Mn, Fe)S content in the steel. However, it takes considerable expense to reduce the sulfur content in the steel and yet it is impossible to reduce the sulfur content to zero. Therefore, other measures must be taken to reduce or prevent the formation of a(Mn, Fe)S. What is the most important in the process of rust formation is the fact that a(Mn, Fe)S is soluble in water. Therefore, the rust formation can be prevented by a primitive method such as by changing the physical properties of a(Mn, Fe)S or by converting this sulfide into other metal sulfide which hardly reacts with water.

From the above point of view, the present inventors have studied the dissolution behaviour .of various sulfides into water, and the results are shown in FIG. 1. These sulfides were separated by electrolytically extraction from hot rolled steel plates containing various metals such as Ce, V, Ti, Mn and sulfur. It is understood from FIG. 1 that the dissolution behaviour into water varies remarkably depending on the kind and type of sulfides.

On the other hand, when the steel sheet is used for Cola beverage cans, it is necessary to increase the sulfur content in the steel and retain the dissolved SH ion in the beverage in order to increase the corrosion resistance. Therefore, for this purpose it is necessary the sulfide present in the steel dissolves into the Cola beverage contrary to the case of improving the rust resistance.

The a(Mn, Fe)S commonly present in commercial steels dissolves in the Cola beverage as well as in water and thus this sulfide is favourable to corrosion resistance in the Cola cans although is not desirable for rust resistance.

The present invention will be described by referring to the attached drawings.

FIG. 1 is a graph showing dissolution behaviours of various sulfides electrolytically extracted from the steel when immersed in water (air saturated) at different temperatures for 20 minutes; and

FIG. 2 is a graph showing dissolution behaviours of the same sulfides when immersed in the blue dye solution (CO atmosphere) for 10- hours.

There are certain sulfides which hardly dissolves in water and at the same time it hardly dissolves in a liguid having pH value of 2-3 such as the Cola beverage.

- Therefore, the present inventors have studies the dissolution behaviour of the various sulfides as mentioned before in a blue dye solution simulated to 'the Cola beverage. The results are shown in FIG. 2. It is understood from FIG. 2 that the dissolution behaviour in the blue dye solution varies remarkably depending on the kind and type of the sulfides. Based on the results shown in FIG. 1 and FIG. 2, the present inventors have developed steel sheets having excellent rust resistance, and further developed steel sheets suitable for carbonate beverage cans such as Cola cans and steel sheets suitable for beer cans by adjusting the properties of the sulfide.

The base steel composition according to the present invention comprises 0.001-Q.15% of C, 0.0l-l.O% of Si, 0.01-1.o% of Mn, cool-0.05% of AI, 0.01 0.5% of Cu, 0.00l-0.04% of P, O.0 02-0.07% of S with addition of Ce in an amount so as to maihtain the weight ratio of Ce/S between 0.1-5.0, with the balance being iron and unavoidable impurities. The basic components of the above composition are iron, carbon, manganese, cupper, cerium and sulfur, and these elements are called as the first group elements.

Next, the basic steel composition may contain one or more of Cr, B, Ni and Ti in addition to the above elements and these elements are called as the second group elements.

In the first group elements, cerium, when present with copper, contributes to improve the rust resistance and particularly when the weight ratio of Ce/S is be-- tween 0.1-50, remarkable rust resistance as well as remarkable corrosion resistance in the. blue dye solution are obtained.

The elements in single of the second group tend to improve the rust resistance and sometimes further improve the rust resistance when the first group elements are present with the second group elements.

Thus the modified steel composition of the present invention comprises 0.00l0.l5% of C, 0.0l-l.0% of Si, 0.01-1 .O% of Mn, 0.00l-0.05% of Al, 0.0l-0.5% of Cu, 0.002-0.07% of S, with addition of Ce in an amount so as to maintain the weight ratio of Ce/S between 0.I-50, and if necessary one 'or more 0.005-1 .O% of Cr, ODS-1.0% of Ni, 0.00l-0.05% of B, and 0.00l-0.l% of Ti.

A further modified steel composition of the present invention comprises three or more ofV, Zr, Pr, Nd and Y in an amount between 0.05-0.7 in total,.correspondingto 02-30% of the sulfur content, with the balance 4 sion resistance in carbonate beverage and beer etc. Namely by the addition of three or more of the above elements it is possible that unique sulfides which assure the requred properties of the steel sheet, or spherical being iron and unavoidable impurities. 5 complex sulfides which. hardly dissolve in water but The above ranges for individual elements in the presdissolve into the blue dye are present in the steel. The ent invention have beendecided as effective ranges content of the above elements and the ratio of the from the points of corrosion resistance mechanical content of these elementsto the sulfur content are properties and steel-making aspects. Thus, carbon is adjusted so as to maintain the rust formation rate less necessary for obtaining required strength of the present than 20% by the QC. tester (explained hereinafter) to inventive steel, but more than 0.15% of carbon lowers maintain the corrosion rate less than 50,u.A/cm in the the elongation and deteriorates the rust resistance'and blue dye solution by the simulate test for determining less than 0.001% of carbon lowers the strength and the rust resistance in the cola beverage, and to maintain elongate the steel refining time, thus deteriorates ecothe metal loss by corrosion in NaCl-citric acid solution nomical aspect and. productivity. Silicon and mangaby the beer can simulation test less than 0.30mg/cm. ;nese are necessary as deoxidizing element in the steel Thus, in the present invention, three or more of V, Zr, making process, more than 0.01% of each of Si and Pr, Nd, Y are added in an amount between 0.050.7 Mn, isrequired, .buttheir excessive contents embrittle in total, and the sulfur content is adjusted to less than the steel and give excessive strengthIThus, their upper 0.07% so that the ratio of the total content to the sulfur limit is set as 1.0% andtheir preferable ranges for Si content is between 02-30. The steel sheet of the above andMn are not less than 0.03% and not less than 0.3% 7 chemical composition according to the present invenrespectively. Aluminium is sometimes added as deoxition is made by melting the starting steel material in an dizing element and for otherpurposes. Excessive addiordinary steel making furnace such as an electric furtion of aluminium ,often forms much inclusions which mace and a converter, using, if necessary, the vacuum causes steel defectsand its upper limit is set at 0.05%. degassing, making ingots by a continuous casting Cu is effective topromote rust resistance in cooperamethod or an ordinary ingot making method, hot rolltion with other elementsbut less than 0.01% of Cu is ing, cold rolling, and annealing (including continuous not effective'and more than 0.50% of Cu embrittles the annealing). As the cases demand, the present inventive steel and deterioratesthe workability of the steel. Resteel sheet may be used in as hot rolled, as hot .garding phosphorus, it is desirable to restrict phosphorolled and normalized or annealed or as cold rolled rusas low as possible, and the range of 0.00l-0.04% is condition. Further, the present inventive steel sheet defined by. considering economic'al restrictions in the may be used as a substrate for surface treated steel steel making process. It is'also desirable to maintain'the sheet. sulfur content as low as possible but the range of Examples of the present invention will be set forth 0.002-0.07% is defined by considering economical under. restrictions in the steel making process.'Cerium fixes Table 1 shows the chemical compositions of the pressurlfur as cerium sulfide or complex sulfide with other .ent" inventive steels and conventional steels, both metal, and formssulfides soluble in the blue'dye solu- 'g'melted in a converter, cast into ingots, hot rolled, cold tion. Thus the cerium content is so limited that the rolled and annealed. Table 2 shows results of corrosion weight ratio 'of Ce/S isfbe tween 0.1-50. Cerium is usu- 40 resistance tests. In particular, Table 2 shows the surface ally accompaniediwi th rare e'arth group elements such condition (A after 3 months indoor exposure of the as lanthanum and, therefore, the present' invention cold rolled annealed sheet, the rust formation (A by covers in its scope' t'hecase 'when cerium contains rare athe' Q.C. tester (dried for 15 minutes, wetted for earth group elements such as lanthanum. The content minutes, maintained for 16 hours with the outer surface .of chromium as optional element is limited to 45 at 20C, the inside surface at 32C and forming dews on 0.005l.0% because the effect on rust resistance enthe inside surface) the rust resistance (B) (blue-dye hancement by chromium becomes remarkable when value) in the blue-dye solution, and the rust resistance chromium is present more than 0.005%,by with 'chro- (C) in the citric acid NaCl solution. Also the surface mium contents more than 1.0% increase the pr'oducconditions after 3 months indoor exposure of cold tion cost. The boron range of 0.00l0.05% is decided rolled steel sheets are shown in Table 2. because less than 0.001% of boron is not effective,-but' (A) in the table represents the ratio of rust for- .more than 0.05% of boron causes embrittlement of the mation to surface for test pieces of 3mm thickness, steel. The nickel content is limited to 0.0l l.:.0% for the 30mm width and 50mm length, (B) represents weight reason that the effect of rust resistance improvement losses after 4 day immersion in 500 ml blue dye soluby nickel becomes remarkable when nickel is present tion (CO atmosphere) of 8cm test pieces, and (C) more than 0.01%, but nickel addition more than 1.0% represents weight losses after 4 day immersion in 500 increases production cost. The titanium range of ml citric acid NaCl solution of 8cm test pieces. 0.00l0.1% corresponds to the titanium amount re- It is clearly understood from the results of (A), (B) aining in the steel in case of Al-deoxidization or Ti 1 and (C) in Table 2 that the present inventive steel deoxydizatio'n alone. sheets have remarkably excellent rust resistance and Three or more of V, Zr, Pr, Nd and Y are added for corrosion resistance as carbonate beverage cans and the'reason that such addition provides steel sheets havbeer cans as compared with the conventional steels. ing excellent rust resistance as well as excellent corro- Table 1 Chemical Composition No.- C Si Mn Al Ce S 7 Cu Others Convenl 0.010

Table 1 -continued Chemical Composition No. C Si Mn 1 Ce S Cu Others tional 2 0.05 0.03 0.2 0.018 Steels 3 0.03 0.05 0.3 0.020 0.15

lnven- 4 0.02 0.01 0.10 0.002 0.02 0.003 0.20 me 5 0.01 0.02 0.10 0.003 0.03 0.002 0.25 Steels 6 0.03 0.01 0.15 0.005 0.02 0.005 0.20

7 0.01 0.01 0.17 0.003 0.02 0.015 0.20 La 0005 8 0.02 0.01 0.16 0.005 0.02 0.020 0.23 La 0.01 9 0.01 0.02 0.20 0.006 0.05 0.003 0.18 Cr 0.03 10 0.02 0.01 0.10 0.005 0.02 0.003 0.03 Cr 1.0 l 1 0.005 0.01 0.10 0.005 0.07 0.003 0.03 Ti 0.003 12 0.005 0.01 0.10 0.005 0.07 0.003 0.20 B 0.005 13 0.02 0.01 0.15 0.01 0.03 0.003 0.03 Ni 0.3 14 0.02 0.01 0.15 0.02 0.05 0.020 0.20 Cr 0.8, B 0.006 15 0.01 0.01 0.15 0.01 0.02 0.002 0.03 Ti 0.003, Cr 0.03 16 0.01 0.01 0.15 0.01 0.02 0.003 0.20 V 0.05, Nd 0.005 17 0.01 0.01 0.15 0.01 0.02 0.003 0.20 V 0.03, Zr 0.02, Pr 0.005 18 0.01 0.02 0.15 0.005 0.02 0.003 0.15 Cr 0.03, V 0.05, Pr 0.005, Y 0.06

Table 2 Rust Formation Rust formation Corrosion Corrosion after 3 months determined by rate in rate in indoor exposure Q.C. tester blue dye citric acid solution NaCl solu- A/cm) tion (mg/cm) cold cold rolled cold rolled cold rolled cold rolled rolled and and and and sheet annealed sheet sheet sheet sheet 1 100 100 100 60 1.1 2 100 100 100 45 1.0 3 80 86 90 47 0.5 4 10 15 10 17 0.30 5 8 13 11 17 0.30 6 8 8 10 0.30 7 7 8 8 10 0.28 8 7 10 10 15 0.15 9 6 10 8 11, 0.18 10 7 11 13 7 0.30 l l 12 18 15 8 0.25 12 7 15 15 11 0.20 13 5 8 10 10 0.18 14 1O 12 8 15 0.28 15 10 10 7 11 0.25 16 8 7 7 10 0.17

What is claimed is:

l. A steel sheet having excellent rust and corrosion resistance, consisting of 0.0010.l5% C, 0.01-1.04% Si, 0.01-1.0% Mn, 0.001-0.05% Al, 0.01-0.5% Cu, 0.0010.04% P, 0.002-0.07% S and Ce in an amount to maintain the weightratio of Ce/S between 01-50, with the balance being iron and unavoidable impurities.

2. A steel sheet having excellent rust and corrosion resistance consisting of 0001-01 5% carbon, 0.01-1.04% silicon, 0.01-1.0% manganese, 0.00 l 0.05% aluminum, 0.01-0.5% copper,

0.001-0.04% phosphorus, 0.002-0.07% sulfur, and cerium in an amount to maintain the weight ratio of cerium to sulfur between 01-50, and one or more elements selected from the group consisting of 0.005-1.0% chromium, 0.01-1.0% nickel,

ble impurities. 

1. A STEEL SHEET HAVING EXCELLENT RUST AND COROSION RESISTANCE, CONSISTING OF 0.001-0.15% C, 0.01-1.04% SI, 0.01-1.0% MN, 0.001-0.05% AL, 0.01-0.5% CU, 0.001-0.04% P, 0.002-0.07% S AND CE IN AN AMOUNT TO MAINTAIN THE WEIGHT RATIO OF CE/S BETWEEN 0.1-50, WITH THE BALANCE BEING IRON AND UNAVOIDABLE IMPURITIES.
 2. A steel sheet having excellent rust and corrosion resistance consisting of 0.001-0.15% carbon, 0.01-1.04% silicon, 0.01-1.0% manganese, 0.001-0.05% aluminum, 0.01-0.5% copper, 0.001-0.04% phosphorus, 0.002-0.07% sulfur, and cerium in an amount to maintain the weight ratio of cerium to sulfur between 0.1-50, and one or more elements selected from the group consisting of 0.005-1.0% chromium, 0.01-1.0% nickel, 0.001-0.05% boron, and 0.001-0.1% titanium, with the balance being iron and unavoidable impurities.
 3. A steel sheet having excellent rust and corrosion resistance consisting of 0.001-0.15% carbon, 0.01-1.04% silicon, 0.01-1.0% manganese, 0.001 0.05% aluminum, 0.01-0.5% copper, 0.001-0.04% phosphorus, 0.002-0.07% sulfur, and cerium in an amount to maintain the weight ratio of cerium to sulfur between 0.1-50, and three or more elements selected from the group consisting of V, Z, Pr, Nd, and Y, in a total amount between 0.05-0.7%, the ratio of said total amount to the sulfur content being from 0.2-30, with the balance being iron and unavoidable impurities. 